The present invention relates to a side airbag apparatus that protects an occupant seated in a vehicle seat with an airbag when an impact is applied to the vehicle from a side, for example, due to a side collision.
The side airbag apparatus is widely known as an apparatus that protects an occupant seated in a vehicle seat when an impact is applied to the seat from a side, for example, due to a side collision. A typical side airbag apparatus includes an inflator and an airbag, which is inflated with inflation gas supplied from the inflator. The inflator and the airbag are accommodated in the outer side of the seat back (backrest) of a vehicle seat.
One known form of the side airbag apparatus includes an airbag having a main inflation portion (a main airbag) and an auxiliary inflation portion (an auxiliary airbag) as disclosed in, for example, Japanese Laid-Open Patent Publications No. 2009-23490 and No. 2009-23494. The names of members inside the parentheses represent the names of members used in Japanese Laid-Open Patent Publications No. 2009-23490 and No. 2009-23494.
The main inflation portion is inflated with inflation gas supplied from the inflator and projects from the seat back to be deployed forward between the occupant and a side wall of the vehicle. Prior to the deployment of the main inflation portion outside the seat back, the auxiliary inflation portion is inflated inside the seat back with inflation gas from the inflator common to the main inflation portion to push the occupant toward the inner side. The main inflation portion and the auxiliary inflation portion communicate with each other via communication ports formed therein. In the above described side airbag apparatus, the inflator is arranged in the auxiliary inflation portion, which needs to be inflated preferentially.
In the above described side airbag apparatus, the auxiliary inflation portion is inflated preferentially before the main inflation portion is deployed forward outside the seat back. The auxiliary inflation portion moves the occupant seated in the vehicle seat toward the inner side to enlarge the space between the occupant and the side wall, thereby facilitating the forward deployment and inflation of the main inflation portion.
However, in side airbag apparatuses in which the airbag is constituted by a main inflation portion and an auxiliary inflation portion as described above, there is a tendency to reduce the volume of the auxiliary inflation portion. Accordingly, it is becoming difficult to place an inflator in the auxiliary inflation portion.
Also, although the auxiliary inflation portion enlarges the space between the occupant and the side wall, the main inflation portion is required to be inflated quickly to be properly deployed in the enlarged space. It is thus important for the inflator accommodated in the auxiliary inflation portion to supply inflation gas to the main inflation portion at an early stage, thereby quickly inflating the main inflation portion. Particularly, in the side airbag apparatuses disclosed in Japanese Laid-Open Patent Publications No. 2009-23490 and No. 2009-23494, the communication ports, which connect the main inflation portion and the auxiliary inflation portion with each other, are located at positions spaced apart from the gas outlet of the inflator. The inflation speed of the main inflation portion is therefore subject to further improvement.